Scenario. The site of your client is going to be hosted on your server. They want also a personalized email address (info@company_name.com) but you don’t mean to run an email server on your server machine.
123-reg.co.uk (there are alternatives) gives you the solution:
- Register the domain company_name.com (for example) with them
- Order the email service from them for the same domain (company_name.com)
- Use the DNS panel that comes with a domain registration
- Point the MX record to their email server
- Point the www subdomain (www.company_name.com) to your server outside their network
